1. Field of the Invention
The present invention relates to a mobile communications system, and more particularly, to a method and apparatus for providing a plurality of services via one channel in a mobile communications system. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for a mobile communications system providing a short message transmission service together with a multimedia multicast/broadcast service, whereby a channel for the short message service and a channel for the multimedia multicast/broadcast service are provided via one physical channel and a control information transmission service for the two channels is provided via a control channel for the multimedia multicast/broadcast service.
2. Description of the Related Art
FIG. 1 is a block diagram of a network structure of a universal mobile telecommunications system (UMTS). Referring to FIG. 1, the universal mobile telecommunications system (hereinafter, referred to as ‘UMTS’) includes a user equipment 1 (hereinafter, referred to as ‘UE’), a UMTS terrestrial radio access network 2 (hereinafter, referred to as ‘UTRAN’) and a core network 3 (hereinafter, referred to as ‘CN’). The UTRAN 2 includes at least one radio network sub-system 4 (hereinafter, referred to as ‘RNS’) and each RNS includes a radio network controller 5 (hereinafter, referred to as ‘RNC’) and at least one base station 6 (hereinafter, referred to as ‘Node B’) managed by the RNC. The Node B 6 includes at least one cell.
FIG. 2 is an architectural diagram of a radio interface protocol between a UE 1 and UTRAN 2 based on the 3GPP (3rd Generation Partnership Project) radio access network specifications. Referring to FIG. 2, the radio interface protocol horizontally includes a physical layer, a data link layer and a network layer and the radio interface protocol vertically includes a user plane for data information transfer and a control plane for signaling transfer. The protocol layers in FIG. 2 can be divided into L1 (first layer), L2 (second layer), and L3 (third layer) based on lower three layers of the open system interconnection (OSI) standard model widely known in the communications systems.
The physical layer as the first layer provides an information transfer service to an upper layer using physical channels. The physical layer is connected to a medium access control (MAC) layer above the physical layer via transport channels through which data are transferred between the medium access control layer and the physical layer. Data is transmitted between different physical layers, and more particularly, between the physical layer of a transmitting side and the physical layer of a receiving side via physical channels.
The medium access control (MAC) layer of the second layer provides services to a radio link control (hereinafter abbreviated RLC) layer above the MAC layer via logical channels. The RLC layer of the second layer supports reliable data transfer and is operative in segmentation and concatenation of RLC service data units (SDUs) sent down from an upper layer.
A broadcast/multicast control (hereinafter abbreviated ‘BMC’) layer schedules a cell broadcast message (hereinafter abbreviated ‘CB message’) delivered from a core network and plays a role in broadcasting the message to UEs existing in a specific cell(s). In a UTRAN, a CB message delivered from a higher layer is additionally provided with information, such as a message ID, a serial number and a coding scheme. The CB message is delivered to an RLC layer as a BMC message and is then delivered to a MAC layer via a logical channel CTCH (common traffic channel). The logical channel CTCH is mapped to a transport channel FACH (forward access channel) and a physical channel SCCPCH (secondary common control physical channel).
The PDCP layer is located above the RLC layer and facilitates transferring data using IP packets, such as IPv4 or IPv6, efficiently in a radio section having a relatively small bandwidth. Toward this end, the PDCP layer performs header compression, a function by which mandatory data header information is transferred to increase transport efficiency in a radio section. The header compression scheme of RFC2507 or RFC3095 (robust header compression: ROCH) defined by IETF (Internet Engineering Task Force) can be used.
Since header compression is a basic function of the PDCP layer, the PDCP layer exists only in a packet service domain (hereinafter abbreviated ‘PS domain’). Furthermore, one PDCP entity exists for each RB in order to provide an effective header compression function to each PS service.
A radio resource control (RRC) layer located on the lowest part of the third layer is defined in the control plane only and controls the logical channels, the transport channels, and the physical channels with configuration, reconfiguration, and release of radio bearers (RBs). An RB is a service offered by the second layer for the data transfer between the UE 1 and the UTRAN 2. Generally, configuring an RB refers to defining the characteristics of protocol layers and channels necessary for providing a specific service and is to establish respective specific parameters and operational methods for them.
A multimedia broadcast/multicast service (hereinafter, referred to as ‘MBMS’) offers a streaming or background service to a plurality of UEs 1 using a downlink dedicated MBMS bearer service. An MBMS is provided during one session, and data for the MBMS is transmitted to the plurality of UEs 1 via the MBMS bearer service during an ongoing session only. A UE 1 performs activation first for receiving the MBMS to which the UE has subscribed and receives the activated services only.
The UTRAN 2 provides the MBMS bearer service to at least one UE 1 using radio bearers. The radio bearers (RBs) used by the UTRAN 2 include a point-to-point radio bearer and a point-to-multipoint radio bearer.
The point-to-point radio bearer is a bi-directional radio bearer and is configured by a logical channel DTCH (dedicated traffic channel), a transport channel DCH (dedicated channel), and a physical channel DPCH (dedicated physical channel) or a physical channel SCCPCH (secondary common control physical channel). The point-to-multipoint radio bearer is a unidirectional downlink radio bearer and is configured by a logical channel MTCH (MBMS traffic channel), a transport channel FACH (forward access channel), and a physical channel SCPCH. The logical channel MTCH is configured for each MBMS offered to one cell and is used for transmitting user-plane data of a specific MBMS to a plurality of UEs.
As illustrated in FIG. 3, a logical channel MCCH (MBMS control channel) in a conventional system is a point-to-multipoint downlink channel used in transmitting control information associated with the MBMS. The logical channel MCCH is mapped to the transport channel FACH (forward access channel), while the transport channel FACH is mapped to the physical channel SCCPCH (secondary common control physical channel). A cell has only one MCCH.
The UTRAN 2 providing MBMS services transmits MCCH information through the MCCH channel to at least one UE 1. The MCCH information includes notification messages, specifically RRC messages related to the MBMS. For example, the MCCH information may include messages indicating MBMS service information, messages indicating point-to-multipoint radio bearer information or access information indicating that RRC connection for the MBMS is needed.
FIG. 4 is a diagram illustrating how MCCH information is transmitted in a conventional method. FIG. 5 illustrates a conventional method for providing an MBMS.
As illustrated in FIG. 4, the UTRAN 2 providing an MBMS service transmits the MCCH information to a plurality of UEs 1 via the MCCH channel. The MCCH information is periodically transmitted according to a modification period and a repetition period.
The MCCH information is categorized into critical information and non-critical information. The non-critical information can be freely modified each modification period or each repetition period. However, the critical information can be modified only each modification period.
Specifically, the critical information is repeated one time each repetition period. However, the modified critical information can be transmitted only at a start point of the modification period.
The UTRAN 2 periodically transmits a physical channel MICH (MBMS notification indicator channel) to indicate whether the MCCH information is updated during the modification period. Therefore, a UE 1 attempting to receive only a specific MBMS does not receive the MCCH or MTCH until a session of the service begins but receives the MICH (MBMS notification indicator channel) periodically. The update of the MCCH information refers to a generation, addition, modification or removal of a specific item of the MCCH information.
Once a session of a specific MBMS begins, the UTRAN 2 transmits an NI (notification indicator) through a MICH. The NI is an indication to a UE 1 attempting to receive the specific MBMS that it is to receive an MCCH channel. The UE 1, having received the NI via the MICH, receives an MCCH during a specific modification period indicated by the MICH.
The MCCH information is control information, specifically RRC messages, associated with an MBMS. The MCCH information includes MBMS modification service information, MBMS non-modification service information, MBMS point-to-multipoint RB information and access information.
A UE 1 attempting to receive a specific MBMS using a point-to-multipoint radio bearer receives MCCH information including radio bearer information via an MCCH and then configures the point-to-multipoint radio bearer using the received information. After configuring the point-to-multipoint radio bearer, the UE 1 keeps receiving a physical channel SCCPCH, to which an MTCH is mapped, in order to acquire data of the specific MBMS transmitted via the MTCH.
FIG. 6 is a diagram for explaining that UTRAN can transmit MBMS data discontinuously via MTCH. As illustrated in FIG. 6, a UTRAN 2 in a conventional system may transmit MBMS data discontinuously via the MTCH. In doing so, the UTRAN 2 periodically transmits a scheduling message to UEs 1 via an MSCH, specifically a SCCPCH carrying MTCH, to which an MTCH is mapped. The scheduling message indicates a transmission start timing point and transmission period of MBMS data transmitted during one scheduling period. The UTRAN 2 should previously inform the UE of a transmission period, specifically a scheduling period, of scheduling information.
The UE 1 obtains the scheduling period from the UTRAN 2 and then receives scheduling messages according to the scheduling period periodically. The UE 1 receives a SCCPCH carrying a MTCH discontinuously and periodically using the received scheduling messages. Specifically, according to the scheduling messages, the UE 1 receives the SCCPCH carrying the MTCH during times for which data is transmitted but does not receive the SCCPCH carrying the MTCH during times for which data is not transmitted. Using the above-described scheme, the UE 1 can receive data efficiently so that battery consumption may be diminished.
A cell broadcast service (hereinafter abbreviated CBS) associated with the BMC layer is a service for exchanging messages configured with characters and numerals between UEs 1, or between a UE and network 3 and is called a short message service (hereinafter abbreviated SMS). An SMS is classified into a cell broadcast short message service (hereinafter abbreviated SMS-CB), which sends a short message to at least one or more cells and a point-to-point Short message service (hereinafter abbreviated SMS-PP). As illustrated herein, the CBS corresponds to an SMS-CB and indicates a service that broadcasts a plurality of CBS messages to all users within a specific area.
A CBS message is a user message configured with characters and numerals. One CBS message is configured with one or more pages up to a maximum of 15. One page is configured with 82-octects that correspond to approximately 93-character information.
CBS messages are broadcast to a geographical area called a cell broadcast area. The cell broadcast area is constructed with one or more cells or an entire Public Land Mobile Network (PLMN). Each of the CBS messages is broadcast to a geographical area by a mutual contract between an information provider and a PLMN operator.
FIG. 7 is a block diagram of a network structure for a cell broadcast service. As illustrated in FIG. 7, CBS messages originate in a plurality of cell broadcast entities 11 (hereinafter abbreviated CBEs) connected to a cell broadcast center 13 (hereinafter abbreviated CBC). The CBE 11 separates the CBS message into a plurality of pages. The CBC 13 is one node of a core network 3 that performs a scheduling function by managing the CBS message.
Iu-BC is an interface defined between the CBC 13 and the RNC 5 using a service area broadcast protocol (hereinafter abbreviated SABP). The CBC can give the RNC a broadcast order for a new message or enable a previous broadcast message to be amended or stopped using the SABP.
The RNC performs a scheduling function for a CBS message delivered by the CBC and a broadcasting function to transmit the message to a specific cell using a BMC protocol. The RNC has a broadcast/multicast interworking function (hereinafter abbreviated BMC-IWF) above a BMC layer to perform an interpreting function for a message and information delivered from the CBC. The UE receives a CBS message broadcast by the UTRAN.
Examples of BMC messages used in the BMC protocol are a CBS message delivering user information, a schedule message facilitating reception of a CBS message by a UE and a CBS41 message delivering a short message delivered from an ANSI41 network. All the messages are transmitted only from the UTRAN to the UE. The UE can reduce its battery consumption by performing a discontinuous reception (hereinafter abbreviated DRX) using information in the schedule message delivered by the UTRAN.
Scheduling BMC messages for transmission is divided into two levels. A first level of scheduling is to determine a frame that can carry data of the CTCH.
FIG. 8 is a diagram for explaining a first level scheduling. As illustrated in FIG. 8, a logical channel CTCH is mapped to a physical channel S-CCPCH via a transport channel FACH. A first level of scheduling designates a frame of a physical channel usable in transmitting data of the logical channel CTCH prior to data transmission.
Numerals in FIG. 8 correspond to System Frame Number (SFN) values. As illustrated in FIG. 8, consecutive M-frames in the data carried over CTCH are always transmitted as a group and this frame group repeats a uniform frame according to a period N. The data carried over CTCH is always transmitted during two consecutive frames and is repeated according to a 6-frame period.
The frame group carrying CTCH data starts when an SFN value is ‘K’ and the frame group is repeated according to a period ‘N’. As illustrated in FIG. 8, “K” is 2 and the frame group starts when an SFN value is 2 and the frame group is repeated according to a period of ‘6’.
The first level scheduling of BMC is performed identically for all CBS services of. Specifically, the same frame is allocated to all CBS services in the same cell. The RRC layer performs the first level scheduling and the value of ‘N’, ‘K’ or ‘M’ is included in the system information broadcast to a UE.
A second level scheduling divides the frame allocated in the first level scheduling into CBS schedule periods. The BMC layer performs the second level scheduling.
The UE receives a BMC schedule message and then acquires information during a CBS schedule time. The BMC schedule message includes information related to a length of the CBS schedule time and a start point of the CBS schedule time. The length of the CBS schedule time indicates a length between a start and an end of the CBS schedule time beginning after the BMC schedule message. The start point of the CBS schedule time indicates a difference between a transmission timing point of a current BMC schedule message and a start timing point of the CBS schedule time beginning after the BMC schedule message.
Therefore, a UE receiving a CBS message can determine when a CBS schedule time, which starts after reception of a BMC schedule message, begins and when the CBS schedule time ends. The UE can acquire information regarding a next CBS schedule time by receiving the BMC schedule message during the CBS schedule time. In this way, the UE can determine when no BMC message is transmitted and the UE can perform DRX in order to conserve battery power.
FIG. 9 is a configurational diagram of a conventional MC schedule message. As illustrated in FIG. 9, a BMC schedule message provides information related to one or more BMC messages that will be transmitted during a next CBS schedule time.
The new message bitmap parameter indicates whether each message transmitted during a next schedule time is a newly broadcast message or corresponds to a repeated transmission of a previously broadcast message. The message explanation parameter indicates information, such as message type and message ID, of each BMC message transmitted during a next CBS schedule time. The message type indicates whether a corresponding message is a CBS message, a schedule message or a CBS41 message.
Using conventional methods, the UTRAN offers MBMS and CBS independently. Specifically, since the MBMS channel and the CTCH channel are provided via different physical channels, if a UE attempts to receive an MBMS and a CBS simultaneously, the UE must receive separate physical channels for the MBMS and CBS.
Therefore, there is a need for a system for effectively radiating the heat generated to prevent problems associated with high temperature, densely packed circuit electrical components of a terminal for a mobile communication system.